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https://issues.apache.org/jira/browse/HIVE-18743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16370276#comment-16370276
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Alexander Behm commented on HIVE-18743:
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Thanks you, [~kgyrtkirk]. I agree completely. I'm very much in favor of getting
rid of all non-obvious side effects of Metastore API calls. Stats collection is
one of those side effects. As is today, it is very hard to reason about what
exactly the Metastore will do how expensive API calls are.
> CREATE TABLE on S3 data can be extremely slow. DO_NOT_UPDATE_STATS workaround
> is buggy.
> ---------------------------------------------------------------------------------------
>
> Key: HIVE-18743
> URL: https://issues.apache.org/jira/browse/HIVE-18743
> Project: Hive
> Issue Type: Improvement
> Components: Metastore
> Affects Versions: 1.2.0, 1.1.0
> Reporter: Alexander Behm
> Assignee: Alexander Kolbasov
> Priority: Major
>
> When hive.stats.autogather=true then the Metastore lists all files under the
> table directory to populate basic stats like file counts and sizes. This file
> listing operation can be very expensive particularly on filesystems like S3.
> One way to address this issue is to reconfigure hive.stats.autogather=false.
> *Here's the bug*
> It is my understanding that the DO_NOT_UPDATE_STATS table property is
> intended to selectively prevent this stats collection. Unfortunately, this
> table property is checked *after* the expensive file listing operation, so
> the DO_NOT_UPDATE_STATS does not seem to work as intended. See:
> https://github.com/apache/hive/blob/master/standalone-metastore/src/main/java/org/apache/hadoop/hive/metastore/utils/MetaStoreUtils.java#L633
> Relevant code snippet:
> {code}
> public static boolean updateTableStatsFast(Database db, Table tbl,
> Warehouse wh,
> boolean madeDir, boolean
> forceRecompute, EnvironmentContext environmentContext) throws MetaException {
> if (tbl.getPartitionKeysSize() == 0) {
> // Update stats only when unpartitioned
> FileStatus[] fileStatuses = wh.getFileStatusesForUnpartitionedTable(db,
> tbl);
> return updateTableStatsFast(tbl, fileStatuses, madeDir, forceRecompute,
> environmentContext); <--- DO_NOT_UPDATE_STATS is checked in here after
> wh.getFileStatusesForUnpartitionedTable() has already been called
> } else {
> return false;
> }
> }
> {code}
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